Cold working is an operation performed on metal components to increase the strength characteristics of that metal component. This operation involves plastically deforming critical portions of the metal component, thereby changing the grain structure therein. This type of operation is commonly used on corner areas of metal components. Such corner areas typically act as stress risers, thereby cracking under extreme loads. The cold working process acts to plastically deform these cornered areas, otherwise known as fillets, to increase the strength characteristics of the particular location.
In crankshaft design, a crankshaft typically has a plurality of fillets located along various points of the crankshaft periphery. Under engine loads, these fillets act as stress risers and if not properly treated, can result in cracking of the crankshaft. As such, typical manufacturers utilize a cold working process on the fillet radii to enhance their strength characteristics. This cold working process typically utilizes a pair of primary rollers which physically contact and deform the fillet radii. To obtain the required force for plastic deformation of the fillet radii, a secondary roller is provided which maintains physical contact and pressure against the primary rollers. This pressure drives the primary rollers into the fillet radii, and thereby plastically deforms the fillet radii.
While this method provides adequate work hardening of the fillet radii, drawbacks exists in regards to the wear characteristics of the primary and secondary rollers. More specifically, the extreme amount of force required by the primary rollers to cause plastic deformation can result in extreme wear between and primary and secondary rollers. This wear requires manufacturers to frequently replace the primary or secondary rollers. As a result, manufacturers are forced to shut down manufacturing lines and replace costly parts. The present invention was developed in light of this drawback.